Fuel cells can be used for powering and/or charging of electronic devices among other applications, which are well known in the prior art. The typical power level for fuel cells used as such power sources is 0.1 to 50 W. A commonly used fuel in this type of fuel cells is hydrogen.
The PEM (Polymer Electrolyte Membrane or Proton Exchange Membrane) fuel cell is one common type of fuel cell. However, such fuel cells are sensitive to high cell voltages, since the lifetime of the cells is negatively affected thereby. High cell voltages leads to carbon corrosion, catalyst dissolution and ionomer degradation. It is therefore desirable to avoid high cell voltages as much as possible. Furthermore, the mixture of O2 (oxygen) and H2 (hydrogen) in the anode compartment has shown to further decrease the lifetime of the MEA (Membrane Electrode Assembly). See reference 1) Review: Durability and Degradation Issues of PEM Fuel Cell Components, F. A. de Bruijn, V. A. T. Dam, and G. J. M. Janssen, Fuel Cells 08, 2008, 1, 3-22, and reference 2) A review of the main parameters influencing long-term performance and durability of PEM fuel cells, Wolfgang Schmittinger, Ardalan Vahidi, Journal of Power Sources, 2008, 180, 1-14.
It is therefore desirable to shorten the time when both hydrogen and oxygen are present in the hydrogen compartment. Furthermore, it is believed that a mixture of hydrogen and oxygen gases in the anode compartment is less detrimental for the MEA if the cell voltage is lowered by e.g. short circuiting the cell. Thus, the time the cells are left at open circuit potential and the time the cells are exposed to a mixture of O2 and H2 should be minimised.